Telephone system



may 12, 1931. s R SMITH 1,805,153

TELEPHONE SYSTEM Filed Sept. 14, 1929 III Um SH 1 REUBEN EffiTTh Patented May 12, 1931 FFICE PATENT SIDNEY REYNELL SMITH, OF LONDON, ENGLAND, ASSIGNOR TO ASSOCIATED TELEPHONE AND TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WAR-E TELEPHONE SYSTEM Application filed September 14, 1929, Serial No.

The present invention relates to impulse sending arrangements, more particularly for use in automatic telephone systems and similar situations. In modern automatic tele- 5 phone systems it is frequently arranged that the impulses for operating the switches used in setting up connections are generated by means of apparatus at the exchange, the impulses generated by a subscriber by means of his dial switch serving merely to operate register switches. This arrangement ensures that the impulses sent to the switches over which the connection is set up shall be'of substantially constant characteristics which could not be the case if the switches were directly operated by impulses sent over subscribers lines of dilferent lengths and grades of insulation. It is important that impulses for operating automatic switches should be generated at a particular speed and also'that they should have a given ratio of make to break if reliable operation of the switches is to be secured. This has generally been attained hitherto by the use of special cams driven at constant speed. In automatic telephone systems employing register translators however it is frequently necessary that impulses shall be generated continuously, and with cam type impulse senders a considerable amount of wear then takes place, and thus the impulse ratio is apt to alter. The object of the present invention is to provide an improved arrangement for supplying impulses of standard speed and ratio to a number of pieces of equipment. For practical reasons it is desirable to provide a pair of impulse springs individual to each piece of equipment but for simplicity of maintenance it is desirable also to provide centralized control so that adjustments of speed and ratio may readily be effected in one operation for all the impulse senders.

According to one feature of the invention use is made of a polarized relay which is alternately energized and de-energized at the required speed by means of alternating current supplied to it.

According to another feature of the invention, impulses are generated by supplying .to a, polarized relay alternating current hav- 392,524, and in Great Britain November 6, 1928.

ing the positive and negative waves of differ:

' posed direct current voltageis variable, for

instance by means of a potentiometer, as this provides an extremely simple and reliable method of altering the impulse ratio. 7

The invention will be better understood from the following description of a preferred embodiment, which should be taken in conjunction with the accompanying drawing. It will be understood, however, that this arrangement'is given by way of example only and that various modifications could be made to the circuit details without exceed ing the scope of the invention. V

Referring now to the drawing, duplicate alternators are provided as shown at 1 and 2 so as to prevent a complete pulse failure in the event of breakdown. The alternator 1 is driven by a direct current motor 3 c0ntrolled by any suitable and well-known arrangement, so as to have constant speed. The alternator Qwhich would preferably be iden tical with thealternator l is driven atthe same speed by a synchronous motor awhich' would preferably be fed from the mains and would normally be in use, while the direct current motor 3 might be arranged to be driven from the exchange battery. lVith this arrangement automatic control gear of known type could be provided whereby in the event of any defect in alternator 2 or in the motor for driving it or a failure of the power supply, alternator 1 would automatically. be brought into service and would continue to" carry the load until the trouble could be rectified; Preferably also arrangements are provided for synchronizing the alternators 1 and 2 and connecting them in parallel to the load over the switches 5 and 6; these synchronizing arrangements however are not shownsince Y they may be of any well-known type. -The polarized relays 7 which could be mounted on or adjacentto equipment. .tcwhi h. th y.

were supplying impulses are preferably connected across a ring main comprising conductors 8 and 9 which are provided at intervals with the disconnecting switches 10 by means of which it is readily possible to cut out a faulty section without affectingthe operation of the remainder. Included in the feed circuit to the ring main is a battery 11 across which is connected a potentiometer 12 by means of which the applied direct current voltage may be varied. The alternators 1 and 2 are conveniently specially designed to provide a substantially pure sine wave though this is not essential and it is of course clear that the magnitude of the direct current voltage must not exceed the" maximum value of the altermating current voltage.

Alternatively the direct current voltage could be supplied from a generator mounted on the same shaft as the alternators, and this might be'of advantage, since any speed variations would similarly affect both the alternatingv and direct current. voltages and would thus be'less liable to'cause an alteration of the impulse ratio.

The operation of the apparatus will be readily followed from what has already been said, and it need be merely pointed out at this time that theefiiect of the superimposed direct current is to give unequal lengths to the-positive: and negative portions of the resultant wave so that the polarized relays which will be energized during one portion and de-energ'ized during the other portion will give attheir contacts impulses of the required ratio. Thepol'arizedrelaysare prefer ably of the moving coil type, the moving coil being traversed by the alternating current While the polarizing coil is traversed by a steady direct current of suitable value.

It will be seen therefore that according to the invention a very simple and satisfactory scheme has been devised for supplying impulses to a number of pieces of equipment whereby the advantagesof individual impulse generators are obtained as regards the comparative constancy of the maximum load together with the advantages of group dri e as regards centralized speed control and means of adjustment.

I claim:

1. In combination, a polarized impulse sired frequency for alternately energizing and deenergizing said relay to generate impulses at a speed corresponding to said frequency, a source of direct current, and means for variably superimposing the direct current on the alternating current to variably alter the duration of the positive and negative wavesot-the alternating current to variably alter the impulse ratio of the impulses generated said; relay.

3. The combination of an alternating current circuit including a source of alternating current and a polarized impulse transmitting relay alternately energized and deenergized by the alternating current for transmitting impulses, and a local direct current circuit included in the alternating current circuit for altering the duration of the positive and negative waves of the alternating current to thereby alter the impulse ratio of the impulses transmitted by said relay.

4. The combination of an alternating current circuit including a source of alternating current and a polarized relay alternately energized and deenergized by the alternating 

